1. Technical Field
The present invention relates to an apparatus and method for coloring extruded products. More particularly, the present invention relates to a novel method and apparatus for varying the coloring and/or flavoring of extruded food products during a single production run of a single extrusion device.
2. Description of the Related Art
The use of extrusion devices is prevalent in a number of industries, especially the food industry. Because of their versatility and efficiency, extrusion devices are often utilized to produce a wide variety of food products such as ready-to-eat (R-T-E) cereals, snack foods and confections. The use of extrusion devices is particularly extensive in manufacturing food products because a single machine can produce large quantities of finished product in a minimal amount of time.
Food manufacturing processes which utilize extrusion devices typically include an extruder device which receives a flowing mass of an edible base substance and conveys it via a screw pump mechanism to an outlet where the substance is forced through an extruder die. Upon exiting the extruder die, the extruded substance may be formed into sheets or cut to a desired dimension by a cutting mechanism. The extruded substance, or extrudate, may thereupon be further processed by, for example, freezing or cooking.
By way of example, in FIG. 1, there is shown a simplified schematic representation illustrating a prior art food manufacturing process utilizing an extrusion device. As is commonly known in the art, such a process typically includes an extrusion device 10, which includes an inlet 12 for receiving a flowing mass of an edible base substance; a main passageway 14, which directs the substance to a screw pump mechanism 18, which further conveys the substance through an extrusion chamber 16 in the direction of arrow ε to an outlet 20 where the substance is forced through an extruder die (not shown). The extrusion chamber 16 is enclosed in an extruder casing 22. The cross-sectional area of the extrusion chamber 16 is typically much greater than the cross-sectional area of the outlet 20 and the extruder die.
Upon exiting the extruder die, the extruded substance may be formed into sheets or cut to a desired dimension by a cutting mechanism (not shown). The extrusion device 10 may also include an additive supply line 24 which allows an additive to be introduced to the substance prior to its conveyance through the extrusion chamber 16 via the screw pump mechanism 18. While being conveyed through the extrusion chamber 16 via the screw pump mechanism 18, the additive is usually thoroughly admixed with the substance prior to reaching outlet 20. A pump mechanism 30 is used to control the flow rate of the additive in the direction of arrow ω from a source 32 to a fluid supply inlet 26 in the extruder casing 22.
Extrusion devices may also impart or extract heat to or from the base substance during its transit through the extruder device. Typically, the casing 22 surrounding the extrusion chamber 16 is adapted to impart or extract heat to or from the substance in accordance with practices commonly known in the art. For example, chiller extruders may be used to chill and thicken a base substance to a desired consistency prior to its extrusion through the extruder dies. Similarly, cooker extruders are used to prepare cooked dough extrudates that may then be formed into individual cereal or snack pieces, and subsequently baked or fried. One variation of cooker extruders that is increasingly popular comprises an extruder wherein the conditions of the extruder and the cooked cereal dough are such that the dough puffs immediately upon being extruded and is cut into individual puffed pieces at the die head. Such a process is referred to generally as “direct expansion” or “puff extrusion.”
Current advances in extruder technology also make it possible for a single extruder device to produce multiple extruded shapes during one production run. For example, instead of using a single extruder die, an extruder device may include a plurality of outlet passageways that divide the original stream into multiple sub-streams, which are each then extruded through a separate extruder die.
While the preparation of a snack food product comprised of multi-shaped, puffed or direct expanded extrudate is desirable, it may also be desirable to produce a mixture of such a product that has different colors, flavors, or similar additives. For example, a snack food blend that includes a mixture of differently shaped pieces may be desirable, with each shape having a distinctive color and/or flavor. The different colors can be used to associate a shape with a particular attribute, such as hot, very hot, savory, sweet, etc. The coloring/flavoring of extruded food products typically comprises either coloring and/or flavoring the base substance prior to its introduction to the extruder device or adding a colorant and/or flavoring to the base substance within the extruder device wherein it is admixed utilizing the screw pump mechanism.
In current practice, in order to produce a snack food blend of distinctive colors, shapes or flavors, a sequence of individual color/flavor/shape production runs are made. The product from each run is collected and subsequently admixed to form the aggregate blend. By way of illustration for a direct expanded snack food product, a first cooked cereal dough is prepared by adding a first color to the starting material or by injecting a first color into the dough upstream of the extrusion die. The first colored dough is directly expanded through a shaped extrusion die and face cut as it expands to form individual pieces. To prepare a second color and shape, the first color injection is discontinued and a second different color material is injected into the cooked cereal dough. To prepare a second shape, the first die head is removed and substituted with a die head having the desired second shape.
While satisfactory, one problem with this conventional practice resides in the generation of unusable scrap material during the color addition transition as the new color is admixed with the residual amounts of the prior color. Still more scrap material is generated as the extruder comes up to steady state conditions after the second color run is started. A second problem is that the various colored pieces must be collected in large batches to be admixed at a later time to form the blended snack food product. The properties (e.g., plasticity, temperature, moisture content, starch conditions, frangibility, etc.) of the finished pieces may deteriorate over the storage period. A third problem relates to the broken pieces, dust and/or cereal fines created by the admixing step.
A variety of proposals have previously been made to remedy the aforementioned problems associated with extrusion devices in producing extruded food products having a blend of distinctive shapes, colors, and/or flavors.
For example, U.S. Pat. No. 5,169,949 to Farnsworth et al. discloses a free-standing die assembly for use in the production of extruded products. The Farnsworth et al. '949 apparatus is mounted as a separate unit apart from the extruder in which product ingredients are processed. In accordance with the Farnsworth et al. '949 invention, hot flowable dough processed in an extruder is carried via suitable tubing to the center plate from where it is distributed to the planar faces of the plate and into the die units, from which it is extruded through the die orifices in the die units. The die assembly may be modified to permit the production of coextruded product from the die orifices in the die units of the assembly. One or more of the die assemblies may be associated with a single extruder. The Farnsworth et al. '949 process may also include injecting and mixing an additive into the conduits carrying the hot flowable dough to one or both of the die assemblies. However, while the Farnsworth et al. '949 patent discloses a means for adding multiple colors to a common extrudate (see e.g., FIG. 4), there are no provision for mixing or varying pre-mixed colorants. Moreover, the Farnsworth et al. '949 device is a fairly complex tubing and die assembly that is mounted as a separate unit apart from the extruder in which the base product ingredients are initially processed.
Other prior proposals include U.S. Pat. No. 5,919,509 to Cremers et al., which discloses an apparatus and method for forming a single extrudable food stream such as a cooked cereal dough into a plurality of differently colored and/or flavored dough streams. The initial plastic food mass (i.e., base substance) is divided into a plurality of substreams by branching a main passageway section into a plurality of sub-divided dough passageways. These sub-passageways are each separately supplied an additive and has disposed therein a multiplicity of in-line static mixer elements to admix the additive into the substream of the plastic food mass prior to extrusion through a die port. While effective, the Cremers et al. '509 device is still rather complicated and offers no variance of coloration/flavoring of each separate substream.
Thus, a need exists for an improved apparatus and associated method for varying the coloring and/or flavoring of extruded food products during a single production run of a single extrusion device. Further, a need exists for an less complicated apparatus and associated method for producing an extruded food product having a blend of distinctive shapes, colors, and/or flavors during a single production run of a single extrusion device.